In an existing process for designing a base station antenna, cables for signal transmission in the base station antenna are all formed based on combination of and interconnection among a strip line, a microstrip, and a coaxial line. A basic composition of the strip line includes, in an outer-to-inner sequence, a strip-line outer conductor (a strip-line ground plane), a strip-line signal cavity, and a strip-line inner conductor. A basic composition of the coaxial line includes, in an outer-to-inner sequence, a coaxial-line outer conductor (a coaxial-line ground plane), an insulation medium, and a coaxial-line inner conductor.
Currently, the strip line is connected to the coaxial line by means of welding or by using a screw. Specifically, in one manner of connecting the strip line and the coaxial line, the coaxial-line outer conductor is first welded to a ground block, and the ground block is connected to the strip-line outer conductor by using a screw. In another manner of connecting the strip line and the coaxial line, the coaxial-line outer conductor is directly welded to the strip-line outer conductor.
In the foregoing two manners of connecting the strip line and the coaxial line, the coaxial line is connected to the strip-line outer conductor by means of welding or by using a screw. Because metal contact and welding are both reasons for generating passive intermodulation interference, when the base station antenna operates in an existing manner of connecting the strip line and the coaxial line, quite a lot of passive intermodulation interference is easily generated. Consequently, communication quality of a communications system is affected. Passive intermodulation refers to an intermodulation effect caused by non-linearity of a passive component when the component operates in a case of multiple high-power carrier frequency signals.